US President Donald Trump has flagged potential concerns over Netflix's planned $72bn (£54bn) deal to buy Warner Brothers Discovery's movie studio and popular HBO streaming networks.

At an event in Washington DC on Sunday, he said Netflix has a "big market share" and the firms' combined size "could be a problem".

On Friday, the two companies said they had reached an agreement that could bring Warner Brothers' franchises like Harry Potter and Game of Thrones to Netflix, creating a new media giant.

The planned deal, which has raised concerns among some in the industry, is yet to be approved by competition authorities. The BBC has contacted Warner Brothers, Netflix and the White House for comment.

Launched in 1997 as a postal DVD rental business, Netflix has grown to become the world's largest subscription streaming service. The deal - the biggest the film industry has seen in a long time - would cement its number one position.

Under the agreement several global entertainment franchises, such as Looney Tunes, The Matrix and Lord of the Rings, would move to Netflix.

The US Justice Department's competition division, which oversees major mergers, could contend that the deal violates the law if the combined businesses account for too much of the streaming market.

At an event at theJohn F. Kennedy Center in the US capital, Trump said that Netflix has a "very big market share" which would "go up by a lot" if the deal goes ahead.

Trump added that he would be personally involved in the decision on whether or not to approve the deal and repeatedly highlighted the size of Netflix's market share.

He also said that Netflix's co-CEO Ted Sarandos recently visited the Oval Office and praised him for his work at the company.

"I have a lot of respect for him. He's a great person," said Trump. "He's done one of the greatest jobs in the history of movies."

Mr Sarandos earlier acknowledged that the agreement may have surprised investors but said it was a chance to position Netflix for success in the "decades to come".

Some in the entertainment industry have criticised the agreement.

The Writers Guild of America's East and West branches called for the merger to be blocked, saying the "world's largest streaming company swallowing one of its biggest competitors is what antitrust laws were designed to prevent."

"The outcome would eliminate jobs, push down wages, worsen conditions for all entertainment workers, raise prices for consumers and reduce the volume and diversity of content for all viewers," it said on Friday.